MHB Mechanics- connected particles

AI Thread Summary
The discussion focuses on calculating tension and acceleration in a system involving connected particles with friction. The initial calculations yield an acceleration of 5 m/s² and a tension of 60 N, which contradicts the textbook answer of 84 N. The user later recalculates the time using the equation S=ut + 1/2at², finding t=1s. Further analysis using the equations Mg - T = Ma and T - mg(sinθ + μ cosθ) = ma leads to a corrected acceleration of 3 m/s² and confirms the tension as 84 N. The thread emphasizes the importance of correctly applying physics equations to resolve discrepancies in calculated values.
Shah 72
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Friction= 1/(sqroot12)×80 cos 30= 20N
I get two equations
T-20=8a and 120-T=12a
a=5m/s^2
I don't know how to calculate the time. Also with this value of acceleration tension value is wrong and the textbook ans is 84N
 
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Shah 72 said:
View attachment 11166
Friction= 1/(sqroot12)×80 cos 30= 20N
I get two equations
T-20=8a and 120-T=12a
a=5m/s^2
I don't know how to calculate the time. Also with this value of acceleration tension value is wrong and the textbook ans is 84N
I calculated the time
S=ut +1/2at^2
(2+1.5)= 1/2×5×t^2
I got t=1s
For q(b) iam getting the ans tension in the rope= 60N but the textbook ans is 84N. Pls help
 
$Mg - T = Ma$
$T - mg(\sin{\theta} + \mu \cos{\theta}) = ma$
———————————————————————
$Mg - mg(\sin{\theta} + \mu \cos{\theta}) = a(M+m)$

$a = \dfrac{g[M-m(\sin{\theta}+ \mu \cos{\theta})]}{M+m} = \dfrac{10\left[12-8\left(\frac{3}{4}\right) \right]}{20}= 3 \, m/s^2$

$T = M(g-a) = 12(7) = 84$N
 
skeeter said:
$Mg - T = Ma$
$T - mg(\sin{\theta} + \mu \cos{\theta}) = ma$
———————————————————————
$Mg - mg(\sin{\theta} + \mu \cos{\theta}) = a(M+m)$

$a = \dfrac{g[M-m(\sin{\theta}+ \mu \cos{\theta})]}{M+m} = \dfrac{10\left[12-8\left(\frac{3}{4}\right) \right]}{20}= 3 \, m/s^2$

$T = M(g-a) = 12(7) = 84$N
Thank you very much!
 
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